Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, so safety is covered. The description adds valuable behavioral detail beyond structured data: partial matching behavior with concrete examples ('Tokyo' resolves to 'Asia/Tokyo', 'NY' resolves to 'America/New_York') and the country-mode behavior of returning all timezones observed in that country.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three focused sentences with no filler. The core purpose is front-loaded, followed by output details and then behavior examples, so the most important information appears first and every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers query modes, return fields, country behavior, and partial matching, while the output schema handles return shape details. For a read-only lookup tool, nothing essential is missing for an agent to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so baseline is 3. The description adds semantic value beyond the schema by illustrating partial-match resolution and clarifying that country mode returns multiple timezones, which helps the agent anticipate return variety.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb plus resource: 'Get timezone info by IANA ID, country code, or partial city/region name.' It clearly differentiates this from siblings like ref_timezone_convert by specifying lookup-oriented outputs such as UTC offset, DST status, and major cities.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives clear context on when to use it: any timezone info lookup by ID, country, or partial name. It also explains mode behavior ('auto tries all strategies') and country-query semantics. It does not explicitly name alternatives or exclusion cases, but the context is specific enough for an agent to apply correctly.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.